Dicarboxylic acids (diacids) are important compounds that are used in the manufacture of commercial polymers (e.g. polyesters, polyurethanes). Recently, methods and compositions for generating diacids by engineering microorganisms to produce diacids have been described (see, e.g., WO2009/121066, incorporated by reference).
The ability to sensitively and rapidly quantify dicarboxylic acid titers from production strains of microorganisms is difficult to accomplish to date. The identification of improved production strains requires variant libraries ranging in size from 102 to 109 to be constructed and screened in an experiment; in general, the larger the library size screened the higher the probability of identifying improved production variants. Screening by liquid chromatography-mass spectrometry, which is the gold-standard in dicarboxylic acid quantification, suffers from low-throughputs and only 102-103 samples can be reasonably analyzed per experiment. Intramolecular excimer-forming fluorescence derivatization was recently demonstrated for detection of dicarboxylic acids in urine samples; the method offers improved throughputs (˜104-105 variants per experiment), but requires extraction with organic solvents, multiple liquid handling steps, and derivatization of the diacid substrate for detection. The above factors impart significant costs that prohibit large-scale implementation of this screening setup. There thus remains need for a low-cost, high-throughput, accurate, and sensitive dicarboxylic acid screening assay. This invention addressed this need.